FOREST STRUCTURE UNDER HUMAN INFLUENCE NEAR AN UPPER-ELEVATION VILLAGE IN NEPAL

Abstract

Across the southern slope of the Nepal Himalaya lie large areas of upper-elevation broadleaf evergreen forest. Resources extracted by subsistence villagers include hand-cut tree-leaf fodder for livestock, fuelwood, and poles for construction of herders’ shelters. Indigenous use of forest products may be altering forest structure and resource availability in Nepal. This research examined forest structure and its relationships with human use of forest products near the upper-elevation village of Chimkhola in west-central Nepal. In the 150-ha forest study area, mean density and standard error (SE) of trees >10 cm dbh was 817 (30) stems ha⁻¹ and mean (SE) total basal area was 44 (3.2) m² ha⁻¹. Cluster analysis of density data for 32 tree species suggested three forest communities: a Symplocos-Quercus community, a Symplocos-mixed evergreen community, and a Rhododendron-Symplocos community. Ordination by principal components analysis of tree species densities indicated a relationship between community structure and a cutting index that increases with harvest intensity. Size-class distributions of important fodder-resource oak species suggested Quercus lamellosa is in decline, but Q. oxyodon and Q. semecarpifolia may be reproducing successfully. Age-diameter regression equations of three evergreen tree species showed growth rate of Symplocos ramosissima to be approximately twice that of Machilus duthei or that of Lindera pulcherrima. The fast growth rate and shade tolerance of S. ramosissima appear to confer a successional advantage. I assessed sustainability of harvest of pole-size (5-10 cm dbh) S. ramosissima used in herders’ shelters, by comparison of harvest and replenishment rates. Mean (SE) density of pole-size S. ramosissima was 375 (32) stems ha⁻¹ in the study area. If the total harvest was distributed evenly across the forest area, it would be 34 stems ha⁻¹ yr⁻¹ and would not exceed the replenishment rate. However, harvest was concentrated in the Symplocos-Quercus community, closest to the village and agricultural fields. Using stump counts as a proxy of relative harvest intensity, harvest rates were sustainable in the Symplocos-mixed evergreen and Rhododendron-Symplocos communities, but not sustainable in the Symplocos-Quercus community.